UMeThe Moody Blues' symphonic-rock masterpiece, Days of Future Passed, was released 50 years ago today in the U.K. and a day later in the U.S. The influential record is a concept album whose songs are connected by orchestral interludes by the London Festival Orchestra.

Longtime singer/bassist John Lodge remembers that when he and his band mates first heard the entire album, they had no inkling that it would be embraced commercially, they were just pleased with what they'd created.

"We didn't know where it was gonna go or where it would take us, or if it would take us anywhere," he tells ABC Radio, "but we were just euphoric, I think, about having the opportunity to make such a wonderful album."

Singer/guitarist Justin Hayward, meanwhile, notes that the success of the album "took us all by surprise."

"None of us expected it to have the success that it did," Hayward tells ABC Radio. "We thought we were making...a limited-appeal kind of album."

Days of Future Passed features perhaps the band's most famous song, the romantic ballad "Nights in White Satin," which Hayward wrote in his teens.

"I was at the beginning of one big love affair and at the end of another one," he recalls. "And I suppose there was a lot of emotions going around in my mind, and…a lot of that stuff just sort of poured out of me."

The Moody Blues have been celebrating Days of Future Passed's 50th anniversary with a tour that was launched in June. The group, just nominated for induction into the Rock & Roll Hall of Fame for the first time, will mount a new U.S. leg of the trek in January. In addition, a deluxe reissue of the album will be released November 17.